If switching from the raid panel to the solo panel and changing from Omen/Recount to Skada both made no difference, you have another problem going on.

By your description of the symptoms and the failure of the usual remedies to make any difference, I'm going to say with 90% certainty that you have a graphics issue. The test is easy enough... does your FPS change notably when you're looking at a blank wall versus when you turn around and look at a busy scene (i.e. the Dalaran fountain area) -- if it does, you have an issue with either your graphics card or the driver.

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What people don't get is that I am, ultimately, an artist at heart. My brush has two colors, 1 and 0, and my canvas is made of silicon.